login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A294124 Numbers k such that (13*10^k + 179)/3 is prime. 0
1, 5, 8, 21, 37, 61, 62, 126, 188, 221, 253, 523, 654, 1875, 2372, 2394, 3073, 4158, 6663, 6881, 167911 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For k>1, numbers such that the digit 4 followed by k-2 occurrences of the digit 3 followed by the digits 93 is prime (see Example section).

a(22) > 2*10^5.

LINKS

Table of n, a(n) for n=1..21.

Makoto Kamada, Factorization of near-repdigit-related numbers.

Makoto Kamada, Search for 43w93

EXAMPLE

5 is in this sequence because (13*10^5 + 179)/3 = 433393 is prime.

Initial terms and primes associated:

a(1) = 1, 103;

a(2) = 5, 433393;

a(3) = 8, 433333393;

a(4) = 21, 4333333333333333333393;

a(5) = 37, 43333333333333333333333333333333333393; etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(13*10^# + 179)/3] &] (* corrected by Georg Fischer, Jul 22 2019 *)

CROSSREFS

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Sequence in context: A138810 A331700 A105634 * A120036 A036381 A277369

Adjacent sequences:  A294121 A294122 A294123 * A294125 A294126 A294127

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Oct 23 2017

EXTENSIONS

a(21) from Robert Price, Nov 17 2018

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 16 09:13 EST 2021. Contains 340204 sequences. (Running on oeis4.)